In sport climbing, a common method of belaying is to use a static rope brake attached to the belayer’s harness, but the belayer can move freely. This paper investigates the dynamics of a climbing fall with such a belayer. The dynamics are nontrivial because of the belayer’s constraint to be always at or above his initial position. An exact solution for a linear elastic rope is presented. Compared to a fix-point belay, one obtains a considerable force reduction on the belay-chain. However, there is a trade-off of a longer stopping distance of both climber and belayer. In order to calculate the stopping distance, friction between rope and the top carabiner has been taken into account. Closed-form formulas allow for calculating the maximum impact force, as well as the minimum mass of the belayer which is necessary to hold a fall from a certain height.

在运动攀岩中，固定绳套的一种常见方法是使用固定在安全绳套的安全带上的静态绳索制动器，但是安全绳套可以自由移动。本文研究了使用这种保护层的攀登跌落的动力学。动态是不平凡的，因为保护层始终保持在其初始位置或之上。提出了线性弹性绳的精确解决方案。与固定点固定装置相比，固定装置固定链上的力明显降低。但是，需要权衡登山者和保护者的停止距离更长。为了计算停止距离，已考虑了绳索与顶部安全扣之间的摩擦。封闭式公式可以计算最大冲击力，以及从某一高度坠落所需的保护层的最小质量。